Adult cardiocytes are routinely prepared by proteolytic dissociation of left ventricular tissue of mature rats. These cells readily convert exogenous substrate to prostaglandins whose composition differs from those obtained by heart perfusion. The objectives of the current proposal are: a. To confirm the identity of prostaglandins and related compounds during incubations of isolated myocytes with arachidonic acid. b. To determine the extent and composition of prostaglandin synthesis in myocytes whose endogenous lipids are prelabeled with (1-14C)-arachidonate. c. To survey the effects of various perturbations on myocyte prostaglandin synthesis. These include epinephrine, bradykinin, insulin, Ca2 plus, hypoxia, cyclic AMP, cyclic GMP, theophylline and acetylcholine. d. To determine the relationship of endogenous prostaglandin synthesis, and exogenous prostaglandin inclusion on myocyte glycogen and triglyceride levels and on cellular lipolytic activity.